Cooling device

ABSTRACT

The invention relates to a device for cooling media or liquids, in particular the inlet air and exhaust gas from a motor vehicle.

BACKGROUND

The invention relates to an apparatus for cooling media or fluids, inparticular charge air and recirculated exhaust gases in exhaust-gasrecirculation systems, in particular for a motor vehicle or for largeengines.

According to the prior art, turbochargers or other mechanicalsupercharging systems, such as compressors or the like, are used toincrease the power of engines by compressing the air which is to be fedfor combustion or the charge air. The fluid, gas or medium, such as inparticular air, which is in the process heated as a result of thecompression operation, is then generally cooled by a charge-air cooler.This is done also in order to further increase the air density and tolimit the combustion peak temperatures. The charge air flows through aheat exchanger, which, by way of example, has ambient air or a coolingmedium flowing through it and is thereby cooled. This allows the chargeair to be cooled to a temperature which is approximately 20–90 K abovethe temperature of the ambient air or is as close as possible to thistemperature.

In apparatuses with exhaust-gas recirculation, the exhaust gas is cooledin a dedicated heat exchanger and is then admixed or fed to the cooledcharge air. This typically results in the temperature of theexhaust-gas/charge-air mixture being higher than the charge-airtemperature at the outlet of the charge-air cooler.

This results in a significant drawback with regard to demands relatingto reduced emissions, in particular of NOx, and reduced consumption,which are certain to rise in future.

SUMMARY

It is an object of the invention to provide an apparatus in which thetemperature of the exhaust-gas/charge-air mixture is reduced compared toknown apparatuses.

According to the invention, this object is achieved by an apparatus forcooling charge air and exhaust gas in particular in a motor vehicle orfor large engines with internal combustion engine, having a recirculatedexhaust-gas stream and a charge-air stream, in which the exhaust-gasstream is cooled by means of a first and a second heat exchanger, thecharge-air stream is cooled by means of a third heat exchanger, beforethe exhaust-gas stream and charge-air stream which have been cooled inthis manner are combined and mixed.

According to a further concept of the invention, the object of theinvention is achieved by an apparatus for cooling charge air and exhaustgas in particular in a motor vehicle with internal combustion engine,having a recirculated exhaust-gas stream and a charge-air stream, inwhich the exhaust-gas stream is cooled by means of a first heatexchanger, the cooled exhaust-gas stream is combined with the charge-airstream, and the mixed exhaust-gas/charge-air stream is then cooled bymeans of a second heat exchanger.

According to a further concept of the invention, the object of theinvention is achieved by an apparatus for cooling charge air and exhaustgas in particular in a motor vehicle with internal combustion engine,having a recirculated exhaust-gas stream and a charge-air stream, inwhich the exhaust-gas stream is combined with the charge-air stream andthe mixed exhaust-gas/charge-air stream is then cooled by means of aheat exchanger.

In this context, it is advantageous if the recirculated exhaust-gasstream can be controlled by means of a valve. A valve of this type maypreferably be a disk valve. However, a different type of valve can alsobe used in other exemplary embodiments of the invention.

Furthermore, it may be expedient if the first heat exchanger and thesecond heat exchanger are formed as separate heat exchangers. In afurther exemplary embodiment, it is expedient if the first heatexchanger and the second heat exchanger, as separate heat exchangers,are formed as a structural unit. Furthermore, in a further exemplaryembodiment it is expedient if the first and/or the second and/or thethird heat exchanger are formed as a structural unit.

According to the invention, it is expedient if at least one of the heatexchangers is cooled by means of a first coolant, such as air, coolant,such as cooling water with or without additives, refrigerant from arefrigerant circuit in particular of an air-conditioning system.

BRIEF DESCRIPTION OF THE DETAILS

In the text which follows, the invention is explained in detail on thebasis of a number of exemplary embodiments and with reference to thedrawing, in which:

FIG. 1 shows an apparatus in accordance with a first exemplaryembodiment of the invention;

FIG. 2 shows an apparatus in accordance with a second exemplaryembodiment of the invention;

FIG. 3 shows an apparatus in accordance with a third exemplaryembodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 shows an apparatus 1 for cooling fluids, such as in particularfor cooling exhaust gas and charge air. The exhaust gas from theinternal combustion engine 2 is discharged through the pipes 3 and, forexample, passed via a turbine 4. Part of the exhaust-gas stream isrecirculated via a valve 5. The recirculated exhaust gas is cooled by afirst heat exchanger 6. At the outlet, it reaches a first temperatureT1. Then, the exhaust gas which has been cooled to T1 is cooled totemperature T2 by a second heat exchanger.

The charge air is compressed by means of the element 4. The compressedcharge air is fed by means of the pipes 8 to a third heat exchanger 9,which cools the charge air to a temperature T3. After it has emergedfrom the third heat exchanger, the cooled charge air is mixed with theexhaust gas, which has been cooled twice, and fed back to the engine 2by means of the pipe 10.

It is advantageous if the exhaust gas in the first heat exchanger iscooled by means of engine cooling water as cooling medium. The secondheat exchanger 7 can then use air, a low-temperature coolant or arefrigerant as cooling medium in order to further cool the exhaust gas.The low-temperature coolant is in this case a coolant at a temperaturewhich is lower than the temperature of the engine cooling water used inthe first heat exchanger.

The two heat exchangers 6 and 7 may in this case be formed as separatelyformed heat exchangers or may be formed as a structural unit. It is alsopossible for one of the two heat exchangers 6 or 7 or both of these heatexchangers to be formed as a structural unit with the third heatexchanger 9. However, the latter may also be formed as a separate heatexchanger.

In the case of heat exchangers which have been combined as a structuralunit, the fluid passages for exhaust gas and charge air are routed andcooled separately.

It is preferable for the heat exchanger 7 to be fixed to the engine orarranged or integrated in a cooling module, in which various coolers,radiators or heat exchangers are combined.

It is preferable for charge air and exhaust gas to be mixed in a mixingchamber 11, which can also be cooled. For this purpose, the mixingchamber may be part of a module or a heat exchanger.

FIG. 2 shows an apparatus 101 for cooling fluids, such as in particularfor cooling exhaust gas and charge air. The exhaust gas from theinternal combustion engine 102 is discharged through the pipes 103 and,for example, passed across a turbine 104 or the like. Some of theexhaust-gas stream is recirculated to the engine 102 via a valve 105.The recirculated exhaust gas is cooled by a first heat exchanger 106. Itreaches a first temperature T1 at the outlet. Then, the exhaust gaswhich has been cooled to T1 is mixed with the compressed charge air fromline 108.

The charge air which has been mixed with exhaust gas is fed, by means ofthe pipes 108 a, to a second heat exchanger 107, which cools the exhaustgas/charge air mixture to a temperature T2. After it emerges from thesecond heat exchanger 107, the cooled exhaust gas/charge air mixture isfed back to the engine 102 by means of the pipe 109.

It is advantageous if the exhaust gas in the first heat exchanger 106 iscooled by means of engine cooling water as cooling medium. The secondheat exchanger 107 can then use engine cooling water, air, alow-temperature coolant or a refrigerant as cooling medium for furthercooling of the exhaust gas/charge air mixture. The low-temperaturecoolant is in this case a coolant which is at a temperature that islower than the temperature of the engine cooling water used in the firstheat exchanger.

The two heat exchangers 106 and 107 may be formed as separately formedheat exchangers or may be formed as a structural unit. If they areformed as a structural unit, the coolers, radiators or heat exchangerscan be formed in such a manner that the media, in particular exhaust gasand charge air, are routed in different fluid passages.

It is preferable for charge air and exhaust gas to be mixed in a mixingchamber 110, which may also be cooled. For this purpose, the mixingchamber may be part of a module or of a heat exchanger.

It is preferable for the heat exchanger 106 and/or 107 to be arrangedfixed to the engine or arranged or integrated in a cooling module inwhich various coolers, radiators or heat exchangers are combined.

FIG. 3 shows an apparatus 201 for cooling fluids, such as in particularfor cooling exhaust gas and charge air. The exhaust gas from theinternal combustion engine 202 is discharged through the pipes 203 andpassed, for example across a turbine 204. Some of the exhaust-gas streamis recirculated to the engine 202 via a valve 205. The recirculatedexhaust gas is mixed with the compressed charge air from pipe 207upstream of the heat exchanger 206.

The charge air is compressed by means of the element 204. The compressedcharge air is fed, by means of the pipes 207, to a mixing chamber 210,in which the charge air and the recirculated exhaust gas are mixed. Themixing chamber 210 may advantageously be cooled. For this purpose, themixing chamber may be part of a module or a heat exchanger.

The mixed exhaust gas/charge air mixture is cooled to temperature T bymeans of the heat exchanger 206.

After it has emerged from the heat exchanger 206, the cooled exhaustgas/charge air mixture is fed back to the engine 202 by means of thepipe 211.

It is advantageous if the first heat exchanger is operated and suppliedby means of engine cooling water, air, a low-temperature coolant or arefrigerant in order to cool the exhaust gas/charge air mixture. Thelow-temperature coolant is in this case a coolant which is at atemperature that is lower than the temperature of the engine coolingwater used in the first heat exchanger. It is also possible for aplurality of the abovementioned coolants to be used in one heatexchanger in order to cool the temperature T of the exhaust gas/chargeair mixture as far as possible. For this purpose, separate circuits areprovided for the coolants in the heat exchanger.

It is preferable for the heat exchanger 206 to be arranged fixed to theengine or to be arranged or integrated in a cooling module in whichvarious coolers, radiators or heat exchangers are combined.

In the exemplary embodiments described, the exhaust gas is recirculatedupstream of the turbine, i.e. the exhaust gas is tapped off upstream ofthe turbine and partially recirculated. In corresponding exemplaryembodiments, it is also possible for the exhaust gas to be tapped offfrom the low-pressure side of the turbine and recirculated.

In exemplary embodiments in which they flow separately through the heatexchangers, the exhaust gas and the charge air may preferably be mixeddownstream of the heat exchanger.

If the exhaust gas and charge air flow through one heat exchanger, theycan be mixed before entering the heat exchanger or in the inlet chamberthereof. It is also possible for the mixing to take place at the end ofthe heat exchanger, in its end chamber, or outside the heat exchanger.

The invention is not restricted only to the exemplary embodimentsmentioned above. It is also possible for individual features of theexemplary embodiments to be combined with one another.

1. An apparatus suitable for cooling charge air and exhaust gas in amotor vehicle with an internal combustion engine, comprising: a firstheat exchanger adapted to cool a recirculated exhaust-gas stream; asecond heat exchanger adapted to cool the exhaust-gas stream, saidsecond heat exchanger located downstream from the first heat exchanger;and a third heat exchanger adapted to cool a charge-air stream, whereinthe apparatus is adapted to combine the exhaust-gas stream andcharge-air stream after the exhaust-gas stream has been cooled by thefirst heat exchanger and the second heat exchanger and after thecharge-air stream has been cooled by the third heat exchanger, andwherein the first heat exchanger and the second heat exchanger areseparate heat exchangers and are formed as a structural unit.
 2. Theapparatus as claimed in claim 1, further comprising a valve adapted tocontrol the recirculated exhaust-gas stream.
 3. The apparatus as claimedin claim 1, further comprising fluid passages that separately route andcool the exhaust gas and the charge air.
 4. The apparatus as claimed inclaim 1, further comprising a mixing chamber that is adapted to combinethe exhaust-gas stream and charge-air stream after the exhaust-gasstream has been cooled by the first heat exchanger and the second heatexchanger and after the charge-air stream has been cooled by the thirdheat exchanger, wherein the mixing chamber comprises a portion of a heatexchanger and is adapted to be cooled.
 5. The apparatus as claimed inclaim 1, further comprising a mixing chamber that is adapted to combinethe exhaust-gas stream and charge-air stream after the exhaust-gasstream has been cooled by the first heat exchanger and the second heatexchanger and after the charge-air stream has been cooled by the thirdheat exchanger, wherein the mixing chamber is part of a heat exchangemodule.
 6. The apparatus as claimed in claim 1, further comprising amixing chamber that is adapted to combine the exhaust-gas stream andcharge-air stream after the exhaust-gas stream has been cooled by thefirst heat exchanger and the second heat exchanger and after thecharge-air stream has been cooled by the third heat exchanger, whereinthe mixing chamber is part of a heat exchanger.
 7. The apparatus asclaimed in claim 6, wherein the exhaust-gas stream and the charge-airstream are mixed at an inlet of the heat exchanger.
 8. The apparatus asclaimed in claim 6, wherein the exhaust-gas stream and the charge-airstream are mixed at an exit end of the heat exchanger.
 9. An apparatussuitable for cooling charge air and exhaust gas in a motor vehicle withan internal combustion engine, comprising: a first heat exchangeradapted to cool a recirculated exhaust-gas stream; a second heatexchanger adapted to cool the exhaust-gas stream; and a third heatexchanger adapted to cool a charge-air stream, wherein the apparatus isadapted to combine the exhaust-gas stream and charge-air stream afterthe exhaust-gas stream has been cooled by the first heat exchanger andthe second heat exchanger and after the charge-air stream has beencooled by the third heat exchanger, and wherein at least two of thefirst and/or the second and/or the third heat exchanger are formed as astructural unit.
 10. The apparatus as claimed in claim 9, furthercomprising a mixing chamber that is adapted to combine the exhaust-gasstream and charge-air stream after the exhaust-gas stream has beencooled by the first heat exchanger and the second heat exchanger andafter the charge-air stream has been cooled by the third heat exchanger,wherein the mixing chamber comprises a portion of a heat exchanger andis adapted to be cooled.
 11. An apparatus suitable for cooling chargeair and exhaust gas in a motor vehicle with an internal combustionengine, comprising: a first heat exchanger adapted to cool arecirculated exhaust-gas stream; and a second heat exchanger adapted tocool a mixed exhaust-gas/charge-air stream that is formed by combiningthe exhaust-gas stream cooled by the first heat exchanger with acharge-air stream, wherein the first heat exchanger and the second heatexchanger are separate heat exchangers and are formed as a structuralunit.
 12. The apparatus as claimed in claim 11, wherein the first heatexchanger and/or the second heat exchanger is fixed to the engine. 13.The apparatus as claimed in claim 11, wherein the first heat exchangerand/or the second heat exchanger is integrated in a cooling module. 14.The apparatus as claimed in claim 11, further comprising a mixingchamber that is adapted to form the mixed exhaust-gas/charge-air streamby combining the exhaust-gas stream cooled by the first heat exchangerwith the charge-air stream, wherein the mixing chamber comprises aportion of a heat exchanger and is adapted to be cooled.
 15. Anapparatus suitable for cooling charge air and exhaust gas in a motorvehicle with an internal combustion engine, comprising: a first heatexchanger adapted to cool a recirculated exhaust-gas stream; and asecond heat exchanger adapted to cool a mixed exhaust-gas/charge-airstream that is formed by combining the exhaust-gas stream cooled by thefirst heat exchanger with a charge-air stream, wherein the exhaust gasis recirculated upstream of a turbine.
 16. The apparatus as claimed inclaim 15, further comprising a mixing chamber that is adapted to formthe mixed exhaust-gas/charge-air stream by combining the exhaust-gasstream cooled by the first heat exchanger with the charge-air stream,wherein the mixing chamber comprises a portion of a heat exchanger andis adapted to be cooled.